Blank cartridge for fastening tools of center fire type



June 30, 1 KAZUMOTO YAMAMOTO 3,139,030

BLANK CARTRIDGE FOR FASTENING TOOLS 0F CENTER FIRE TYPE Filed March 28, 1961 KAZUMOTO YAMA MOTO INVENTOR.

ATTORNE VS United States Patent 3,139,030 BLANK CARTRIDGE FOR FASTENING TOOLS OF CENTER FIRE TYPE Kazumoto Yamamoto, Nobeoka-shi, Japan, assignor to Asahi Kasei Kogyo Kabushiki Kaisha, Osaka, Japan, a corporation of Japan Filed Mar. 28, 1961, Ser. No. 98,942 Claims priority, application Japan May 4, 1960 1 Claim. (Cl. 102-45) This invention relates to cartridges for fastening tools, and more particularly to cartridges which do not need small arms primer. Also it relates to the improvement in the conventional cartridge of center fire type.

The usual cartridges for fastening tools are roughly classified into two groups; one is the so-called center fire type which has a priming chamber at the bottom of a case, the other is the rim fire type which has a priming composition inserted into a space around the bottom of a case and this bottom is impacted by a firing pin of fastening tools to cause firing.

For the cartridge of center fire type, a case having a priming chamber had to be prepared. There were, therefore, some defects due to the complexity of the structure of the case and the higher cost derived from the use of the small arms primer which needed much labour in manufacturing. In the cartridge of rim fire type, it was very diflicult to put the priming composition into the space of the bottom of the case. Consequently, the probability of miss fire in the finished cartridges was very high. It had been thought difficult to manufacture the cartridge which fires exactly and does not cause a back fire no leak of a gas from the bottom, particularly with the cartridge for big size fastening tools which requires a large amount of the powder charge.

The cartridge of the present invention is manufactured at a lower cost because it is not necessary to prepare the priming chamber, nor the small arms primer is used in manufacturing the case, and the priming composition is charged more exactly into a zone of shock of impact as compared with a cartridge of rim fire type, with the result the firing becomes more exact and also can prevent a back fire completely.

In order to achieve the above-mentioned objects, the present invention comprises a cartridge in which a cavity is provided at the center of the bottom of a cartridge case, a priming composition in said cavity, and an anvil having a projection at the center and having more than one flash hole around the projection, said anvil being fixed on said priming composition. The projection of the anvil is positioned so as to be located at the center of the cavity in the case bottom. Therefore, when the anvil is inserted therein in a definite position, said projection is embedded in the priming composition in said cavity.

Accordingly, with the present invention, it is possible to obtain practically innumerable improved results for the following reasons:

Since the cavity is provided at the center of the case bottom, it is possible to charge the priming composition into a precise position to be impacted by a firing pin of the fastening tool, i.e., in the center of the case bottom.

Since the cavity is provided in the case and the projection of the anvil is so fixed as to be embedded in the priming composition in said cavity, any clearance between the bottom of anvil and the upper surface of the filled priming composition is made smaller, so that any danger caused by the falling of the priming composition is minimized even after inserting the anvil.

Further, since the cavity is provided in the cartridge case, it is not necessary to charge a large amount of priming composition, whereby the increment of gaseous pressure due to an excess of priming composition, and a break- 3,139,030 Patented June 30, 1 964 age of the case caused by the increment of gaseous pressure can be prevented.

The greatest characteristic of the present invention is that the projection of the anvil is so fixed as to be embedded in the priming composition in the cavity. Due to this structure, the distance between the case bottom and the projection on the anvil is minimized and hence percussion energies are concentrated so as to act on the projection of the anvil, whereby the firing sensitivity is markedly increased.

The invention will now be described with reference to the accompanying drawings, in which:

FIG. 1a is a sectional elevation view of a cartridge case according to the present invention;

FIG. lb is a sectional view taken on line 1a1a of FIG. 1a;

FIG. 2a is a sectional elevation view of a modification of the cartridge case according to the present invention; and FIG. 2b is a sectional view taken on line 2b-2b of FIG. 2a.

In FIG. 1a a cartridge case 1 is provided with a cavity 2 at the center of the bottom 1a and the edge of the open end 7 is bent inwardly, said cavity 2 being filled with a priming composition 3. In the cartridge case 1 is an anvil 4 having a projection 10, and segmental flash holes 5 on both sides of the projection, as is clear from the sectional view shown in FIG. lb. The anvil 4 is fixed inside the cartridge body 1 by means of an upwardly open tubular extension 9 pressed against the inside of the tubular case, so that the projection 10 is embedded in the priming composition 3 in the cavity 2. A powder charge 6 is placed in the cartridge body 1 and is held :in by a paper disk 8.

FIG. 2a shows a structure similar to FIG. la, wherein a cartridge case 1 has a cavity 2 at the center of the bottom and the edge of the open end 7 is bent inwardly, and said cavity 2 is filled with a priming composition 3. As shown in FIG. 2b, the anvil 4 has a projection 10 at the center of the bottom and small circular flash holes 5 are provided on both sides of the projection 10. The anvil 4 is press fitted inside the cartridge body 1 by means of an upwardly open extension 9 so that the projection 10 is embedded in the priming composition 3 in the cavity 2. The powder charge 6 is placed over the anvil 4, and a paper disk 8 holds it in the casing 1.

As mentioned above, in the present invention, the cavity is provided at the center of the case bottom with the priming composition in said cavity, and moreover the projection on the anvil is embedded in the priming composition in said cavity. Therefore, when compared with the conventional cartridge, which employs a small arms primer, the cartridge of the present invention is not only readily manufactured at a low cost, but has the advantage of being capable of preventing completely a backfire be-.

cause the so-called detonator chamber for inserting the small arms primer is not required to be provided.

Material used for the cartridge and the anvil is a metallic one conventionally utilized, for example, brass, copper, iron, aluminum and the like. The priming composition employed herein may be the one known as used for small arms primer, and composed mainly of mercury fulminate-potassium chlorate-antimony trisulfide, lead thiocyanate-potassium chlorate-fine glass powder, or others. The powder charge employed herein may be of either double or single base, and be the one conventionally used for a cartridge of guns.

Accordingly, when a firing pin of the fastening tool impacts and shocks the case bottom, the priming composition is fired by this shock and the firing flame causes the burning (or ignition) of the powder charge through the holes of the powder charge chamber.

3 What I claim is: A center fire type cartridge which comprises a tubular cartridge case made of metal and having an open end and a bottom with a cavity at the central part of the bottom and opening into the casing, a priming composition in said cavity, a tubular anvil having a bottom with flash holes therethrough and an outward projection at the center of the bottom, the tubular portion of said anvil being inserted in the cartridge case and tightly pressed against the inside of the tubular cartridge case with the projection on the bottom of said anvil embedded in the priming composition in the cavity of said case bottom with thetportion of the projection embedded in the priming composition and spaced from the bottom of the 4 cavity a distance less than the depth of the cavity, a powder charge in said case on said anvil, and a paper disk covering the end surface of said powder charge adjacent the open end of the cartridge case.

References Cited in the file of this patent UNITED STATES PATENTS Re. 9,453 Cranston Nov. 9, 1880 87,735 Van Vechten Mar. 9, 1869 1,438,779 Olin Dec. 12, 1922 2,518,958 Thomson et a1. Aug. 15, 1950 FOREIGN PATENTS 505,761 Germany Aug. 25, 1930 

